This invention relates generally to a device for restricting at all times differential movement of side gears of a differential gear for an automobile, and more particularly to a restriction device for a differential gear of the type wherein prebiasing springs are disposed between the opposite inner end surfaces of each side gear in a differential casing and multi-plate clutches are provided between the outer cylindrical surfaces of each side gear and the inner surface of the differential casing such that each plate of the multi-plate clutches comes into strong contact with each other and creates frictional resistance among each adjacent plate by resilient force of the springs.
The restrictive performance of differential movement by the multi-plate clutches in such a restriction device of differential gear employing prebiasing springs is greatly dependent upon the resilient force of the prebiasing spring. Accordingly, when the wear amount of each friction plate forming the multi-plate clutches is large, the resilient force of the prebiasing springs is changed or decreased, and as the result, the frictional torque of the multi-plate clutches is changed or decreased.
In the case of a restriction device for a differential gear not employing prebiasing springs, when the wear amount of each friction plate forming the multi-plate clutches is large, wear particles exist on the friction plates. This causes undesired noise to be created in a differential gear.